A macro file must have a name in the form name.tmac or
tmac.name and be placed in a tmac directory to be
found by the -mname command-line option.5
Together, these directories constitute the tmac path. Each
directory is searched in the following order until the desired macro
file is found or the list is exhausted.
troff’s or groff’s
-M command-line option.
GROFF_TMAC_PATH environment variable.
HOME.
/usr/local/lib/groff/site-tmac /usr/local/share/groff/site-tmac /usr/local/share/groff/1.23.0/tmac
The foregoing assumes that the version of groff is 1.23.0, and
that the installation prefix was /usr/local. It is possible to
fine-tune these locations during the source configuration process.